Molybdenum Blue (ascorbic acid reduction): At a pH of ca. 1, ammonium molybdate reacts with phosphate forming colourless molybdophosphoric acid. Upon reduction with ascorbic acid it turns into the blue compound phosphoromolybdenum blue. The intensity of the colour is related to the phosphate concentration.

Number of Tests

70

Interferences

Water constituents at concentrations commonly found in natural waters will not cause interferences. Various heavy metals (e.g. Nb, Ta, Sn, W, Ti, Zr, Bi) can cause serious interferences. Seawater and waters high in salinity will not interfere.

Measuring Range

The standard measuring range is 0 – 0.4 mg/L phosphate-phosphorus. The colour comparator has 5 colour fields: 0–0.05–0.1–0.2–0.4 mg/L. For higher phosphorus concentrations, the sample has to be diluted. A 1:5 sample dilution can be carried out easily, thus extending the measuring range to 2 mg/L.

Shelf Life

2 years

Applications

Determination and monitoring of phosphorus levels in natural waters including brackish water and seawater (environmental monitoring).